*2.4.3.2.4 Sublethal effects of acaricides on reproductive performance of females and subsequent generation*

Acaricides, abamectin and fenpyroximate caused an overall reduction of *P. plumifer* population by increasing pre-oviposition period, decreasing oviposition period, decreasing fecundity in both treated female and their offspring. The number of eggs laid by treated female was so affected in both abamectin and fenpyroximate treatment. The total laid eggs were 46.57 eggs in control that decreased to 0.57 and 1.08 eggs in LC20 and LC30 treatment of abamectin and fenpyroximate, respectively. The treated females with LC30 of abamectin laid no egg (**Figure 3**).

#### **Figure 3.**

*Effects of sublethal concentrations of acaricides (fenpyroximate and abamectin) on fecundity of* Phytoseius plumifer. *Different small letters above each bar indicate a statistically significant difference between concentrations. Different capital letters above each bar indicate a statistically significant difference between acaricides (P < 0.05) (LSD).*

#### *2.4.3.2.5 Sublethal effects of acaricides on demographic parameters*

The intrinsic rate of increase (*r*m) is based on both survivorship and fecundity. So it has been recommended to use for evaluating the total effects of pesticides [51]. Our results along with several other studies have reported that life-table parameters of phytophagous and predatory mites were affected by sublethal concentrations of acaricides [36, 39, 45–47]. In our study, the life-table parameters showed significant differences, in population growth and reproductive performance, between offspring from females treated with sublethal concentrations of acaricides (fenpyroximate and abamectin) and untreated females of *P. plumifer* even in the

#### **Figure 4.**

*The intrinsic rate of increase (rm) of offspring of the treated and untreated females of* Phytoseius plumifer. *Different small letters above each bar indicate a statistically significant difference between concentrations. Different capital letters above each bar indicate a statistically significant difference between acaricides (P < 0.05) (LSD).*

#### **Figure 5.**

*Total voracity of treated and untreated females of* Phytoseius plumifer*. Different small letters above each bar indicate a statistically significant difference between concentrations. Different capital letters above each bar indicate a statistically significant difference between acaricides (P < 0.05) (LSD).*

*Biological Control of Tetranychidae by Considering the Effect of Insecticides DOI: http://dx.doi.org/10.5772/intechopen.100296*

lowest concentration (LC10). The intrinsic rate of increase (*r*m), (**Figure 4**) the net reproductive rate (*R*0) and the finite rate of increase (*λ*) of the offspring of treated females with both acaricides were markedly lower compared with the offspring of untreated females. This in turn resulted in a longer doubling time (*DT*). Moreover, in our laboratory observations the decrease in *r*m values in sublethal concentrations maybe due to reduction of the mating rate and mobility of the offspring from treated females than untreated ones [36, 39].
